The measurement of load of a vehicle may be provided for a large-sized vehicle such as a truck, etc., for example, for the purpose of preventing traffic accidents such as rolling accidents caused by overload, etc., and preventing acceleration of deterioration of the vehicle.
Conventionally, the measurement of load of a vehicle is performed in the condition that the vehicle, which is a subject of the measurement, is placed on a platform weighing machine so called "KANKAN" in Japanese. However, because a large-scaled equipment and a large installation space are required for the measurement, the number of platform weighing machines allowed to be installed in the space is limited so that numbers of vehicles cannot be measured. Furthermore, the cost for installing the platform weighing machines increases.
Recently, therefore, a load measuring apparatus which is mounted on the vehicle per se to measure the load of the vehicle is provided.
In an on-vehicle type conventional load measuring apparatus, for example, load measurement sensing devices such as strain gauge sensors, or the like, are designed to be attached to suitable positions between front, rear, left and right places of carrier frames and circular-arc-like leaf springs interposed between left and right opposite end portions of front and rear axles so that the load is measured on the basis of the sum of signals outputted from the sensing devices respectively proportional to the loads imposed on the front, rear, left and right sensing devices.
When the outputs of the respective sensing devices are used directly for the measurement of the load of the vehicle by the aforementioned load measuring apparatus, the outputs of the sensing devices may become values which do not correspond to the loads actually imposed on the respective sensing devices because of the variations in the output characteristics of the sensing devices even in the case where the center of gravity of a baggage is located substantially at a center of a carrier so that the load from the baggage or carrier is evenly imposed on the respective sensing devices. That is, there is a risk that the correct values of the load of the baggage placed on the carrier cannot be obtained on the basis of the sum of the outputs of the respective sensing devices.
Further, the outputs of the sensing devices depend also on vehicle characteristics defined in accordance with the structure of the vehicle.
In measurement of a load on a vehicle by using such a plurality of sensing devices, it becomes necessary to correct the outputs of the sensing devices in accordance with the individual output characteristics and vehicle characteristics.
As described above, calculation of correction values for correcting the output characteristics of the respective sensing devices and calculation of the output correction values of the respective sensing devices in accordance with the vehicle characteristics are performed on the basis of calculation of coefficients to make the sum of the outputs of the respective sensing devices accord with a value corresponding to a known load value in the condition that the value of the load on the carrier is known. Particularly, correction values corresponding to the output characteristics of the sensing devices are calculated after the loaded state is adjusted so that the center of gravity of the carrier in the loaded state is made coincident with the center of gravity of the carrier in the tare or non-loaded state.
Both the calculation of the output characteristics of the sensing devices and the calculation of the output correction values of the sensing devices in accordance with the vehicle characteristics are performed each time by suitably increasing/decreasing the weight value of a weight on the carrier.
That is, the calculation of the output correction values of the load measurement sensing devices is equivalent to the calculation of correction values or correction equations for the sensing devices on the basis of a database constructed by calculation of the changes of the output characteristics of the respective sensing devices corresponding to the weight. It is therefore necessary to fetch the outputs of the respective sensing devices to construct the database while the load on the carrier is increased/decreased gradually and while the load per se after the increase/decrease is always made known.
Therefore, in order to make the load per se after increased/decreased always known while the load of the carrier is increased/decreased gradually at the time of the work of calculating the output correction values, it is considered that weights such as balance weights. etc., each having a known mass value are placed on a single position or a plurality of places on the carrier so that the load is evenly imposed on the sensing devices and the number of weights per place is increased/decreased equally whenever the outputs of the sensing devices have been measured and fetched as data.
Because such balance weights to be used by being mounted on the carrier are, however, large both in weight and in external size, a conveying apparatus such as a forklift, a crane, etc. must be used separately for carrying the balance weights and increasing/decreasing the number of the balance weights on the carrier. Accordingly, there is a disadvantage that not only surplus labor and equipment are required but also dangerous work such as slinging work for the balance weights must be carried out in the case of a crane.
Further, the weight per balance weight is predetermined so that the pitch for increasing/decreasing the load is limited by the predetermined balance weight. There arises a disadvantage that the change of the output of each sensing device cannot be calculated in a pitch smaller than the weight of one balance weight or various kinds of balance weights different in weight must be prepared in order to calculate the change of the output in a pitch as small as possible.
Taking the aforementioned circumstances into consideration, a first object of the present invention is to provide a method of constructing a database for correcting outputs of a plurality of load measurement sensing devices such as strain gauge sensors, etc., for measuring load of a vehicle so that the database is used for calculating correction values for correcting the outputs of the sensing devices in accordance with output characteristics of the sensing devices and vehicle characteristics, and so that the database indicating the output characteristics of the sensing devices can be constructed by simple labor.
A second object of the present invention is to provide a weight vessel adapted for carrying out the database constructing method so that the weight can be changed in a desired arbitrary pitch without requiring any surplus labor, any equipment such as balance weights, and any dangerous work.